Method _forEachExpansionKey

src/cdk/tree/tree.ts:1151–1170

Invokes a callback with all node expansion keys.

(callback: (keys: K[]) => void)

  /** Invokes a callback with all node expansion keys. */
  private _forEachExpansionKey(callback: (keys: K[]) => void) {
    const toToggle: K[] = [];
    const observables: Observable<T[]>[] = [];

    this._nodes.value.forEach(node => {
      toToggle.push(this._getExpansionKey(node.data));
      observables.push(this._getDescendants(node.data));
    });

    if (observables.length > 0) {
      combineLatest(observables)
        .pipe(take(1), takeUntil(this._onDestroy))
        .subscribe(results => {
          results.forEach(inner => inner.forEach(r => toToggle.push(this._getExpansionKey(r))));
          callback(toToggle);
        });
    } else {
      callback(toToggle);
    }
  }

  /** Clears the maps we use to store parents, level & aria-sets in. */
  private _clearPreviousCache() {